DETERMINATION OF ISOPRENE IN HUMAN BREATH BY THERMAL-DESORPTION GAS-CHROMATOGRAPHY WITH ULTRAVIOLET DETECTION

We describe a new, highly sensitive and specific method for the analys is of isoprene (2-methyl-1,3-butadiene) in human breath. A known volum e of expired air (150 mi) was drawn through a solid sorbent material t o capture trace organic substances, followed by thermal desorption at 200 degrees C and subsequent determination of isoprene by gas chromato graphy with diode-array ultraviolet detection. The calibration plot wa s linear (r = 0.99) over a wide range of breath isoprene concentration s (0-12 nmol/l), and levels down to 0.10 nmol/l were easily measurable . In sixteen healthy subjects (six men and ten women), all of whom wer e non-smokers, the mean, median and spread of breath isoprene concentr ations were 3.73, 3.36 and 1.60-10.33 nmol/l, respectively. No statist ically significant differences in the concentrations of breath isopren e were observed between the sexes. The mean ( +/- S.D.) concentration of breath isoprene in nine consecutive tests with the same subject was 3.69 +/- 0.60 nmol/l, and the coefficient of variation was 16.3%. Muc h larger variations in exhaled isoprene were seen during the day and a lso between days when the same subject was tested repeatedly. The excr etion patterns of isoprene in human breath can be investigated with hi gh selectivity and sensitivity with this new analytical method.